The invention relates to the field of semiconductor device manufacture. In particular, the invention relates to processes for ensuring alignment of devices utilized in semiconductor device manufacture.
Devices used in exposure of photosensitive materials during processes involved in semiconductor device manufacture typically require very precise alignment to ensure proper exposure and subsequent alignment of features formed on a semiconductor substrate. Alignment of is photolithographic tools increases in importance as feature sizes decrease and feature densities increase. Misalignment of photolithography tools can result in high rework levels and low yielding product.
Photolithography tool alignment systems may be monitored with a variety of monitoring schemes. For example, alignment repeatability tests, such as field image alignment (FIA), laser scan alignment (LSA), and laser interferometer alignment (LIA), may routinely be run as diagnostics. These processes involve directly and indirectly detecting positions of a support stage for supporting a semiconductor substrate relative to the exposure optics or illumination source. The test may detect the position of one or more fiducial marks on a support stage, on a test element to be supported by the support as a semiconductor substrate would be supported, or on the semiconductor substrate itself.
Often, during periods of high misalignment, the diagnostic processes described above may not indicate a problem. The inventors have determined that when a stage problem exists, intermittent misalignment may occur and the above-described diagnostic tests may not be effective as typically carried out.
The present invention solves this and other problems by providing a method of diagnosing alignment of a photolithography tool. According to the method, a broad band source test is provided. A disturbing sequence is run that is not a portion of the broad band source test. The broad band source test is performed. Post disturbed test data is recorded. A result of the performance of the broad band source test is compared with a tolerance. If the result is not within the tolerance, the photolithography tool is mechanically adjusted.
The present invention also provides a method of diagnosing alignment of a photolithography tool. The method includes performing a broad band source test and recording first test data. A disturbing sequence is run that is not a portion of the test. A second broad band source test is performed and second test data recorded. The result of the second broad band source test is compared with the results of the first broad band source test. If the results of the second broad band source test is not within a tolerance of the results of the first broad band source test, the use of the photolithography tool is stopped and the tool is mechanically adjusted.
Furthermore, the present invention provides a method of diagnosing alignment of a photolithography tool. The method includes performing a first alignment test to determine alignment of the photolithography tool. A second alignment test is performed to determine alignment of the photolithography tool. Test data are recorded from the second alignment test. The test data are compared with a tolerance value. The photolithography tool is mechanically adjusted if the test data is not within the tolerance value range.
Additionally, the present invention provides an article of manufacture that includes a computer usable medium having computer readable program code embodied therein for diagnosing alignment of a photolithography tool. The computer readable program code in the article of manufacture includes computer readable code for causing a computer to run a disturbing sequence. Additionally, the computer readable program code includes computer readable code for causing a computer to perform a broad band source test and record post disturb test data. Also, computer readable code is included for causing a computer to compare a result of broad band source test with a tolerance. Furthermore, computer readable code is included for causing a computer to cause the mechanical adjustment of the photolithography tool if the result of the comparison is not within the tolerance.
Still other objects and advantages of the present invention will become readily apparent by those skilled in the art from the following detailed description, wherein it is shown and described only the preferred embodiments of the invention, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not as restrictive.